1. Field of the Invention
The present invention relates to a light source bulb of a lighting device for a vehicle structured such as to longitudinally slide only a glass tube so as to switch between a high beam and a low beam.
2. Description of the Related Art
Since a high intensity discharge (HID) has only one luminous source, in order to switch between a high beam and a low beam by one luminous source, it is necessary to slide a light source bulb in a direction of an optical axis, as is known in Japanese Patent Application Laid-Open No. 2000-40414. Particularly, the structure is made such that a plate holding a bulb is provided in an attaching portion of a lamp housing, the plate is urged toward a low beam position by a spring, and the plate is moved backward toward a high beam position by a solenoid provided in an outer portion of the lamp housing. That is, when turning on the solenoid, a whole of the light source bulb is moved backward so as to form the high beam, and when turning off the solenoid, the whole of the light source bulb is moved forward due to a spring force so as to be switched to the low beam.
However, in the related art described above, since the whole of the light source bulb is moved by the solenoid provided in the outer portion of the lamp housing, a slide resistance between the light source bulb and the lamp housing is increased, and a position of the luminous portion (a filament and an electric discharge portion) is changed during the movement, so that there is a risk that a predetermined light distribution pattern can not be obtained.
Accordingly, there can be considered a structure in which only the glass tube among the light source bulbs is longitudinally slid without longitudinally sliding the whole of the light source bulb. However, in the case of connecting a harness introduced to the light source bulb itself from the external portion to the glass tube within the light source bulb, the harness is bent at each time of longitudinally sliding the glass tube, so that a deterioration of the harness is caused. Further, in order to longitudinally slide the glass tube while bending the harness, a large driving force is required in correspondence thereto, and a size of a power source (a motor, a solenoid or the like) for driving the glass tube and a power transmission mechanism is increased, so that an increase of size of a whole of the lighting device for the vehicle. Accordingly, it is expected to provide an electric power supply structure for the glass tube which prevents the harness from being deteriorated and generates no slide resistance.
The present invention is made by taking the problems in the related art described above into consideration, and an object of the present invention is to provide a light source bulb of a lighting device for a vehicle which can supply an electric power to a glass tube while preventing a deterioration of a harness and generating no slide resistance even in a structure of sliding only the glass tube.
In accordance with a first aspect of the present invention, there is provided a light source bulb of a lighting device for a motor vehicle which is mounted to a lamp base portion on the basis of a standard set for the light source bulb for the motor vehicle, comprising: a cylindrical lamp base flange attached to the lamp base portion; a case integrally or separately formed in a rear portion of the lamp base flange and having a space sequential to the lamp base flange; a slider received within the lamp base flange in a state of being capable of sliding in a longitudinal direction; a glass tube fixed to a front portion of the slider; and a driving portion received within the case and connected to the slider so as to longitudinally slide the slider.
In accordance with the invention described in the first aspect, since only the glass tube fixed to the slider is longitudinally slid, in an inner portion of the lamp base portion, no great slide resistance is generated at a time of sliding the glass tube, and an accuracy of position of the glass tube is high. Further, the driving portion for moving the glass tube can be achieved by a compact structure which can be received within the light source bulb, so that the size of the lighting device is never increased. Since the light source bulb corresponds to the standard of the lamp base portion, it is not necessary to change the lamp base portion to a structure that does not meet the standard, so that general-purpose properties can be made high.
Further, the structure may be made such that the glass tube is positioned within a substantially cylindrical fixed shade fixed to the lamp base flange, and a notch portion for allowing a light divergence upward from the glass tube is formed in an upper portion of the fixed shade.
In accordance with this structure, since the fixed shade is fixed to the lamp base flange, it is possible to shut out the downward light which reflects by a lower portion of a reflector so as to form an upward glare light.
Further, the structure may be made such that a movable shade forward extended to the above of the glass tube is formed in an upper portion of the slider so as to shut out the light diverging to an oblique rear direction from the glass tube on the basis of a predetermined orientation property.
In accordance with the structure described above, since the movable shade moving together with the glass tube is formed in the upper portion of the slider, it is possible to always shut out the light diverged to the oblique rear direction from the glass tube on the basis of the same orientation property even when sliding the glass tube in the longitudinal direction. Accordingly, it is possible to securely irradiate the light which is reflected by the upper portion of the reflector from the glass tube so as to form a high beam orientation and a low beam orientation, on the basis of an ideal orientation pattern.
Further, the structure may be made such that the lamp base flange except the front portion to which a waterproof cap is closely attached and a waterproof property can be secured, and a case are formed so as to have a waterproof structure.
In accordance with the structure described above, since the rear portion of the lamp base flange out of the waterproof area achieved by the waterproof cap and the case are formed in the waterproof structure, there is no problem in the case that the driving portion including an electric system is received within the case. As the waterproof structure, there can be employed a coating by a waterproof tube in a boundary portion between the lamp base flange and the case, an interposition of a seal member or an O-ring to the boundary portion, an integral formation between the lamp base flange and the case, and the like.
Further, the structure may be made such that the driving portion is formed as a bidirectional solenoid.
In accordance with the structure described above, since the driving portion is the bidirectional solenoid and an electric current application time is short, there is generated no thermal problem even in the case that the driving portion is received within the case.
Further, the structure may be made such that the driving portion is a piston which longitudinally slides due to an air or an oil within the case.
In accordance with the structure described above, since the driving portion is the piston driving within the case, the driving portion is electrically free and is strong against a moisture and an impact. It is possible to widely secure an amount of slide, and it is possible to obtain a greater slide force than the solenoid.
Further, the structure may be made such that the glass tube is of an HID type and the standard of the lamp base portion corresponds to H4.
In accordance with the structure described above, the HID bulb can be replaced while satisfying a beam switching performance of the lighting device for the motor vehicle set on the basis of the H4 bulb. Further, since the lamp base shape corresponds to the standard of the H4 bulb, the waterproof structure can be commonly used as the waterproof cap before being replaced, and it is possible to replace without providing a specific structure, so that it is possible to improve the general-purpose properties. The structure is not limited to the H4 bulb, and the same effect can be obtained in the case of HX bulb.
Further, the structure may be made such that a protrusion and a groove are engaged between an inner surface of the lamp base flange and an outer surface of the slider so as to prevent the slider from rotating, and an air vent is formed in a gap between the protrusion and the groove.
In accordance with the structure described above, since the air can have access from the air vent even when a sealing density is increased in order to increase an accuracy of position between the inner surface of the lamp base flange and the outer surface of the slider, it is possible to smoothly slide the slider. Further, it is possible to properly slide along a baffle.